Your argument would be valid if this phenomenon was specific to USA, but it’s not. It’s happening (to my knowledge) everywhere where kids were given unrestricted access to the Internet. That’s the common denominator, not political or social issues.
That we also have political and social issues is not making the situation easier, but I don’t believe that’s the root cause for kids’ increased mental issues. The previous generations had their part of alarmism and issues as well – e.g. world wars, nukes, oil crises, cold war, smaller wars everywhere all the time (Korea and Vietnam even constituted a general draft in the US, which must have not been a great time), satanism panic/red scare/gay scare.